Vacancy-impurity complexes in polycrystalline Si used as gate electrodes of HfSiON-based metal-oxide-semiconductors probed using monoenergetic positron beams

摘要

Vacancy-impurity complexes in polycrystalline Si (poly-Si) used as a gate electrode of the metal-oxide-semiconductor field-effect transistor (MOSFET) were probed using monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and the positron lifetimes were measured for poly-Si(150 nm)/HfSiON(5 nm)/Si. In addition, first principles calculations were used to identify impurities coupled with defects in the poly-Si film. The major defect species in the poly-Si film was identified as vacancy-type defects; their mean open volume was close to that of a divacancy. Vacancy-oxygen complexes were observed in the P-implanted poly-Si film after annealing (at 1000 ℃); the number of oxygen atoms coupled with each defect was estimated to be one or two. For the B-implanted poly-Si film, however, the formation of the complexes was suppressed, suggesting the formation of oxygen clusters or precipitate. We discuss the interaction between such oxygen-related defects and boron in terms of the electric properties of p-channel MOSFETs.